Technical Abstract:
Kidney inhibition swab (KIS) tests, recently adapted by the US FSIS for antibiotics on-site screening, were employed to evaluate the depletion of penicillin-G residues from kidney, liver, muscle, serum, and urine of sows after intramuscular (IM) penicillin-G procaine administration. Sows (n=130; 227.0 +/- 30.8 kg) were provided daily IM doses of penicillin-G (33,000 U/kg bw; 5x the label dose) for 3 consecutive days using 3 separate administration patterns and six sows per treatment. Sows were slaughtered after 5, 10, 15, 20, 25, 32, or 39 day withdrawal periods. Residues depleted most rapidly from liver and skeletal muscle and the slowest from kidney and urine. Kidney was the most appropriate target tissue for detecting penicillin-G residues in carcasses, with two positive results after a 39-day withdrawal period. These data support a 15-day withdrawal period for penicillin-G treated sows though kidneys may need to be excluded from human consumption.